RS232 vs ITU-T V.24 Signal Names¶

DTE: Data Terminal Equipment (Computer/Terminal)
DCE: Data Communications Equipment (Modem/TA)

There are unfortunately a lot of different terms/names used for serial interfaces, depending on which context/spec you are looking at.

This table provides a mapping of the most common signals between different specs:

Common Name	RS232	ITU-T V.24	Direction	Description
GND	AB	102	-	Signal/System Ground
TXD	BA	103	DTE->DCE	Transmitted data
RXD	BB	104	DTE<-DCE	Received data
RTS	CA	105	DTE->DCE	Request to Send
CTS	CB	106	DTE<-DCE	Clear to Send
DSR	CC	107	DTE<-DCE	Data Set Ready
DTR	CD	108/2	DTE->DCE	Data Terminal Ready
DCD	CF	109	DTE<-DCE	Data Carrier detect
-	-	113	DTE->DCE	Transmitter signal element timing (DTE source)
-	-	114	DTE<-DCE	Transmitter signal element timing (DCE source)
-	-	115	DTE<-DCE	Receiver signal element timing (DCE source)
RI	CE	125	DTE<-DCE	Ring Indicator
-	-	133	DTE->DCE	Ready for receiving

Full ITU V.24 table¶

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